1. Fill four 250 mL (1 cup) jars with blueberries, leaving 1 cm (½ in.) of space at the top.
2. In a saucepan, bring remaining blueberries, maple syrup and cider vinegar to a boil. Cook for a few minutes until the blueberries burst.
3. In a food processer, blend mixture until smooth. Pour coulis into the jars of blueberries. Mix with a wooden spoon to remove air bubbles. Clean jar rims. Close jars without over-tightening the rings.
4. Place jars in a pot of hot water. Carry out a heat treatment for 15 minutes, turn off heat and let jars sit in water for 5 minutes before removing.

Chef’s secret 

The acidity of the brine lets you use the boiling water technique to can the blueberries. 

• Sterilize the jars by immersing them in boiling water for about 5 minutes. The flat lids should be new to ensure a proper seal. They should be soaked in hot water before use.
• Fill the jars, leaving a 1 cm (½ in.) space at the top.
• Close the jars with their lids and rings without overtightening.
• Immerse the jars in a pot of water, ensuring they are at least 2.5 cm (1 in.) under the surface. Cover and bring to a boil over high heat. Let boil according to the recipe instructions.
• Remove jars from water and let stand for 24 hours. The lids should be depressed and make a small popping noise: this means the jars are properly sealed.
• The jars can be stored for one year in a dark, dry, cool place.